The present invention relates to high purity cobalt chloride that is useful as a precursor of CVD materials for producing semiconductor devices and has a higher purity than conventionally by using and electrolyzing cobalt having a purity that can be used as the raw material of cobalt chloride, as well as to the manufacturing method of such high purity cobalt chloride.
Conventionally, cobalt chloride has been used as the raw material of catalysts, organic pigments, dry-wet indicators, magnetic materials and the like. All of these items are demanded of high purity cobalt chloride.
For example, when producing high purity cobalt powder by reducing hydrogen from cobalt chloride, and using the obtained high purity cobalt powder as a magnetic material target, elimination of the following impurities is required.
(1) Alkali metals such as Na (sodium) and K (potassium), and alkaline-earth metals such as Ca (calcium)
(2) Gas components such as C (carbon) and O (oxygen)
(3) S (sulfur)
The impurities described in (1) to (3) entail the following problems.
Since alkali metals such as Na and K and alkaline-earth metals such as Ca easily migrate within the insulating film, they cause the deterioration in the insulation resistance.
Gas components such as C and O cause the generation of particles during sputtering.
S causes the deterioration in the material strength of the target and becomes the source of corrosion of the target.
As an example of a manufacturing method of cobalt chloride, there is Patent Document 1 below. Patent Document 1 describes a manufacturing method of cobalt chloride of using cobalt having a favorable purity level as the anode, using a diluted hydrochloric acid aqueous solution as the electrolytic solution, and electrolytically dissolving the cobalt anode at an acid concentration of 5N (normality) to pH of 1, cathode current density of 5 A/dm2 or less, while maintaining the temperature to be 60° C. or less.
Nevertheless, Patent Document 1 has a problem in that cobalt becomes electrodeposited onto the cathode plate, and this may result in the deterioration of the production efficiency. Moreover, the achieved high purity level is 2N5 (99.5 wt %), and there is no choice but to say that the high purity level is low.